1. Field of the Invention
The present invention relates to a hydraulic non-stage transmission including a swash plate plunger pump and a swash plate plunger motor, wherein a pump discharge port and a pump suction port of the swash plate plunger pump are connected, respectively, to a motor suction port and a motor discharge port of the swash plate plunger pump through a hydraulic closed circuit.
2. Description of Background Art
As to hydraulic non-stage transmissions including a hydraulic pump and a hydraulic motor in combination, a variety of forms of configurations have been known and put to practical use. For example, a hydraulic non-stage transmission are disclosed in Japanese Patent Laid-open No. Hei 6-2753 and Japanese Patent Publication No. Hei 7-88884 which have been proposed by the present applicant. The hydraulic non-stage transmission disclosed in these patent documents includes a swash plate plunger pump, a swash plate plunger motor, and a hydraulic closed circuit for connecting a discharge port and a suction port of the swash plate plunger pump to a suction port and a discharge port of the swash plate plunger motor, wherein a pump swash plate member is driven by an engine, a pump cylinder and a motor cylinder that are connected to each other and disposed in a connected state on an output shaft. A motor swash plate member is restricted in rotation, and the motor swash plate angle can be variably regulated.
In this type of hydraulic non-stage transmission, the pump cylinder and the motor cylinder are connected to each other in a back-to-back relationship with pump and motor distribution valves (distributor valves) disposed at the connected portion, thus forming the hydraulic closed circuit. The pump and motor distribution valves are so configured that an oil discharged from a pump plunger reciprocated in the pump cylinder according to the rotation of a pump swash plate driven to rotate is supplied into a motor cylinder chamber to push the motor plunger. Thus, the motor plunger is moved in the axial direction in sliding contact with a motor swash plate, whereby the motor cylinder is driven to rotate.
Meanwhile, the pump and motor distribution valves are formed by inserting valve spools respectively in a plurality of pump and motor valve spool holes formed to extend radially in the connected portion of the pump and motor cylinders, and providing a pump-side eccentric cam mechanism for reciprocating the pump valve spool according to the rotation of the pump swash plate. A motor-side eccentric cam mechanism is provided for reciprocating the motor valve spool according to the rotation of the motor cylinder. This portion, however, is complicated in structure, and results in a high manufacturing cost.